Biological explanation of OCD

• What are the two types of biological explanations for OCD?

  Genetic and Neural
• What did Lewis (1936) observe in his patients with OCD?

  21% had siblings with OCD and 37% had parents with OCD.
• What conclusion did Lewis (1936) make about this observation?

  OCD runs in families however it’s not certain you will develop OCD just by having relatives with this disorder. OCD is caused by candidate genes which are triggered (according to the diathesis-stress model)
• What is a candidate gene of OCD?

  5HT1-D is an identified gene which is responsible for the disruption in serotonin absorption across synapses.
• What did Taylor (2013) find out about genes involved in causing vulnerability of OCD?

  He conducted a meta-analysis and found over 230 genes responsible for OCD. therefore this disorder is polygenic.
• a group of genes may cause OCD for one person and a different group of genes will also cause OCD in another person, what is this called?

  aetiologically heterogenous, it means the cause of OCD and the type varies from person to person.
• what are neural explanations of ocd?

  the neurotransmitters and structures in the brain are affected by the candidate genes.
• what’s the role of the neurotransmitter serotonin?

  regulating moods. the deeper processing in the brain is often regulated through serotonin, so the lack of serotonin absorbed through the post-synaptic neuron, is what triggers the faulty decision making system.
• How is the decision-making system in OCD faulty?

  The caudate nucleus is thought to be damaged, so it can’t suppresses messages from the orbital frontal cortex, allowing the thalamus to become over-excited so it re-sends signals back to the orbital frontal cortex. this causes impulsive behaviour.